Spray arms in dishwashers comprise a hollow element, typically an elongated hollow element made of sheet metal or plastic, having a plurality of spray nozzles, through which a cleaning liquid can be sprayed against articles to be cleaned.
During a washing cycle, the cleaning liquid usually is circulated continuously through the washing compartment. Thus, the cleaning liquid, such as water to which a detergent has been added, is sprayed by means of rotating spray arms onto articles that are located within the washing compartment. Upon having dripped from the wetted articles to the floor of the washing compartment, the cleaning liquid is collected in a sump of the dishwasher to again be fed by means of a circulation pump to the spray arms.
Although the cleaning liquid on its way to the circulation pump has to pass several filters, such as a coarse filter located around the drain of the sump, and a fine filter that covers a portion of the floor of the washing compartment, from time to time larger dirt particles contained in the cleaning liquid manage to bypass the filters and thus are fed to the spray arms. Given that the nozzles of the spray arm have a small opening diameter, there is a high likelihood that such dirt particles get stuck in one of the nozzles and thus block the flow through the nozzle.
A blockage of the nozzles not only may lead to a poor cleaning result in the specific area of the washing compartment to be covered by the blocked nozzle, but also can deteriorate the overall washing result in case that the blocked nozzle is adapted to provide for a momentum to set the spray arm into rotation, such as by ejecting a water jet at an angle to the axis of rotation of the spray arm.
In order to overcome the above problems, the prior art has made several attempts to prevent larger dirt particles from reaching the spray arm, such as by providing for improved filters in the sump of the washing compartment.
Furthermore, in U.S. Pat. No. 4,210,285 it was suggested to specifically design the channels within the spray so as to guide long slender objects, such as toothpicks, in such a manner towards the spray nozzles, that they do not get stuck within the flow channel but are ejected through the nozzle.
While the earlier attempts may have alleviated the above problems, they were unable to overcome these problems. Thus there still exists a need in the art for improvements so as to avoid larger dirt particles, and in particular dirt particles having a size so that they cannot pass the spray nozzles, from reaching the spray nozzles.